Ambient backscatter: Free energy harvesting from TV signals, to power a ubiquitous internet of things

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Researchers at the University of Washington have created a new method of wireless networking that allows devices to communicate with each other without batteries or their own source of power. Dubbed “ambient backscatter,” this method sucks power out of the air from TV and cellular transmissions, and then modulates this signal with its own data. These modulated signals are then picked up by other devices in the same ambient backscatter network. Requiring a battery or other source of power is probably the most prohibitive factor when it comes to the ubiquity of electronic technology. In theory, this could be the breakthrough to finally allow for a ubiquitous internet of things, where every location is blanketed with devices and sensors that communicate with each other, creating truly smart homes, offices, and cities.

You may or may not realize this, but much of the Earth is blanketed in high-power radio waves, mostly from television and cellular towers. These towers pump out broadcast RF radiation that is picked up by your TV or mobile phone. There’s no “intelligence” or sophistication in such a method — the radio waves aren’t targeted directly at your television set or phone. The waves are just floating around in the atmosphere, waiting to be plucked out of thin air by a receiver that’s tuned to the right frequency. In most cases, the receiver then processes these radio waves into useful data, which is then displayed on a screen or played through an earpiece.

What the University of Washington researchers have done, however, is quite different. They have created a device that has an antenna tuned to UHF TV signals (539MHz in this case), but instead of displaying a picture, the signal’s energy is harvested to power a small device. The device contains logic chip that controls the impedance (resistance) of the antenna. By altering the impedance of the antenna, the TV signal is reflected (backscattered) back into the atmosphere in a specific and controllable way. In other words, the device can generate a signal of its own — a signal that can be picked up by other local devices — without its own source of power, simply by reflecting TV signals in a clever way.

So far, the researchers have created multiple prototype devices, each around the size of a credit card, that use ambient backscatter to communicate with each other, at 1Kbps over 2.5 feet (76cm) outdoors and 1.5 feet (46cm) indoors. This might not sound very good, but 1 kilobyte per second is more than enough for sensor networks, or smart devices in your home/office — and for a prototype, 2.5 feet is pretty good. You only need to get it up to six or 10 feet to make a ubiquitous network, an internet of things, feasible. It goes without saying, too, that these ambient backscatter devices are cheap and easy to produce, too; as you can see in the picture above, it’s essentially just an antenna and a simple microcontroller.

At this point, you’re probably wondering whether it’s actually legal to leech energy from TV signals, and more importantly whether you’re actually allowed to transmit your own signals on a licensed UHF TV band. According to the researchers, their ambient backscatter devices fall under the same governance as another very popular battery-free device: RFID tags. Because these devices emit RF radiation at incredibly low levels (microwatts), and because they’re not actively generating a signal in a reserved block of spectrum, they’re not regulated by the FCC. In the research paper [PDF], they also test whether these ambient backscatter devices interfere with TV signals — and as long as it’s at least 7.2 inches (18cm) away from the TV antenna, no interference is seen. This is partly due to the low output power of the transponder, but also because broadcast TV protocols already account for multipath distortion — that is, signals arriving at different times, depending on atmospheric obstructions (buildings, clouds, mountains, etc.)

Moving forward, it’s possible to make the ambient backscattering devices smaller by using different antenna topologies (meandered, folded dipole), and increased bandwidth could be obtained by using a larger frequency band (again by modifying the antenna). Relying on TV signals and other sources of RF radiation is ingenious, and in large parts of the world can provide almost-guaranteed sources of power. This really could be the technology that finally enables us to put sensors on everything, and to turn every normal object into a smart object that can interact with every other object and computer on the internet. You’ve seen what happens when billions of people are persistently online thanks to mobile phones; now imagine what would happen if you added billions of traffic signals, cars, supermarket shelves, refrigerators, and air conditioning systems to the mix.

Yes, it was included in the free energy episode, but they were able to power what I think I remember was an alarm clock radio with this long antenna that they streched out across their shop.

Phil

Sure, but that’s not really what a “free energy” device is. You need some physics to know what’s going on, but this energy is siphoned off of energy that has been broadcast – it’s not “free” as defined by those hoaxes. That’s why the article mentions concerns that it would interfere with signals.

It’s no more free energy than solar cells. Imagine broadcasters are shining a light from far away, and you’re harvesting a small amount of that when it reaches your receiver.

not flabby

show me several of these in a 8×8 bonded configuration for instance with each using many nanoscale fractal antenna’s ,printed on a super cheap plastic role to role process then we are talking, of course ,just because you can put something like these on everything including choc wrappers so you get lots of dispertion of these devices over time as people drop their litter everywhere doesn’t mean you should…

Freelance_Human

The type of energy emitted by wires and batteries is required to power stuff. We know that it’s dangerous for our bodies to touch, be penetrated by, or absorb the energy emitted by wires and batteries. Next is an obvious point but I feel that conscious thought tends to ignore it: it is not the physical wire nor the physical battery that is dangerous; it is the invisible energy those items emit that is dangerous. So: why would it be okay for energy-by-whatever-name (e.g., RF-EMF, microwaves, WiFi, et al.) that can power stuff to be constantly touching and penetrating into our bodies?

Indeed, in their final sentence “now imagine what would happen.” Hellooooo… that’s already what happens. In a way, devices have SAR (the only difference is that the devices WANT to be penetrated by and absorb the stuff and react to it). That’s the problem … the non-natural non-ionizing radiation penetrates into our BODIES (which are wireless devices that WANT some NATURAL non-ionizing radiation) even though our bodies are “without batteries or their own source of [non-natural electrical] power,” and our bodies absorb those penetrations and react to them in ways that our bodies think are “smart” [the right thing to do, i.e., instigating whatever is the best healthy reaction to something foreign (be it beneficial or not beneficial)].

Postulative

You are already being bombarded by the energy these tap into. They aren’t creating any additional energy, so there is no additional “bombardment”. This technology is just using what is already around, in the same way that solar panels harness light/heat energy.

Of course, in saying this I have ignored your claim that “it’s dangerous for our bodies…”. We live in a high-energy universe, and life has developed based on that environment. This idea that “all this energy must be bad for us” is totally lacking in evidence.

Chris Shakal

Your tinfoil hat is a little crooked there.

John Cisco

Well this is the sort of tech that we need to ensure a fully decentralized banking system for example based on bitcoin. Until connectivity in a utterly pervasive in-escapable manner is there, the crypto currency’s will never be able to hold up against real cash.

i could be wrong, cash is cash and i like the folding type anyways

Jamie MacDonald

I think the NSA just squeed.

Gábor Héja

Great article, thanks! Just one thing, the actual speed they’ve reached is 1 kilobit per second, not 1 kilobyte (the lowercase “b” denotes bit, not byte (also, the kilo is “k”)).

Jeremy Cook

Wow, that is a pretty cool idea! Wasn’t a similar principle used to pick up AM radio signals back in the day?

originalone

All things considered here, can D.A.R.P.A. be in the shadows on this too? After all, it seems that it funds almost ever kind of research, but I’ve noticed that unless one gets into the original papers, then who the sponsors/funding providers are, remains out of sight, though that used to be available at the end of the articles. Space wasted/saved, by the people who reprint, or another of the so-called secrets the Government demands?

oOXOo

This is great but I suspect they won’t be broadcasting TV signals all that much longer, though cell towers will only be growing in numbers & power.

http://disqus.com/sdmitch16/ sdmitch16

They could resuse those bands for free government provided internet. It could have a built in emergency broadcast system so that any device trying to use it would be given data pertaining to the emergency, hopefully video which I think would be doable since it could transmit the same signal to all devices much like tv already does. People could click links that appeared to find information specific to them, their location, allergies, if their power’s out, if they need food or water, if they have a pet. It’d be better than current tv emergency broadcast systems. A tv cost a minimum of $100 and a tuner adds $35. A Koby Kyros tablet is $40. Add an antenna to catch the former tv waves and you now have the best way to get emergency broadcast to the poor ever made.

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